1. Technical Field of the Invention
The present invention relates to sewing machines. More particularly, the present invention relates to a sewing machine for forming a "lock stitch" in a fabric.
2. Discussion of the Prior Art
Sewing machines for forming "lock stitches" in a fabric are known. For example, the Union Special Corporation makes a "lock stitch" sewing machine which is exemplary of the heretofore known "lock stitch" sewing machines. These known "lock stitch" sewing machines includes a reciprocally-mounted needle bar, a needle thread take-up lever, and a rotary hook assembly mounted beneath the needle bar. The rotary hook assembly includes a rotary hook base and a cylindrical bobbin case holder concentrically disposed within the cylindrical hook base and a finger device for holding the bobbin case holder stationary. In the known sewing machine, in order to form a "lock stitch", the rotary hook base makes two revolutions per each cycle of the needle bar, and the needle thread engagement distal end of the needle thread take-up lever moves in an arcuate path upwardly twice as fast as it moves in the downstroke. Therefore, the heretofore known "lock stitch" must operate at high speeds.
A more complete detailed description of these heretofore known "lock stitch" sewing machines is given in the following detailed description.